Many emergency vehicles are equipped with lights that project illumination in a fixed direction, for example, forward of the vehicle, or to the sides of the vehicle. For greatest effectiveness, it is helpful for the first responder to have a source of illumination, such as a spotlight that can be moved to direct light in a desired direction. To be effective, the spotlight must be movable over a wide range of trajectories about a horizontal axis and a vertical axis.
In the past, police and other emergency vehicles have been equipped with spotlights that are directed by means of a mechanism that is installed through a hole in the “A” pillar, a structural member of the vehicle in front of the driver's door and at the left edge of the windshield. Another “A” pillar is located in front of the passenger door at the right edge of the windshield. In older model vehicles, the “A” pillar was a relatively large member formed from mild steel. The required hole was formed using a drill, and the effect on the structural integrity of the “A” pillar was not a large concern.
FIGS. 1-3 represent the functionality of a prior art mechanical control for a spotlight 2. The mechanism to control the spotlight employs an L-shaped handle on the inside of the vehicle. Mechanical force is transmitted from the L-shaped handle mechanism to the spotlight 2 by two concentric shafts 3, 4 that pass through an opening in the “A” pillar. The outer shaft 3 is coupled to the entire handle mechanism, while the inner shaft 4 is coupled to the grip portion 5 only. Application of lateral forces to the grip 5 rotates the entire handle, outer shaft 3 and inner shaft 4, which moves the spotlight 2 over an arc 6 as shown in FIG. 1. The inner shaft 4 is coupled to the grip 5 and to the spotlight 2 by beveled gears so that rotation of the grip 5 about its own axis applies rotational force to the inner shaft 4 and rotates the spotlight 2 about an axis parallel with the grip axis.
When the spotlight 2 is in a vertical orientation, rotation of the grip 5 applies rotational forces to the spotlight 2 to direct the beam laterally (left-right) in a generally horizontal plane about a vertical axis A. This movement may be referred to as “panning” the spotlight. In the prior art mechanical control, an up-down, or “tilt” movement of the spotlight 2 is not possible when the spotlight 2 is in a vertical orientation, which corresponds to the grip 5 being in a vertical orientation (pointing downward inside the vehicle). Moving the grip 5 laterally applies rotational force to the outer shaft, which moves the spotlight 2 along arc 6 from the vertical position to left and right horizontal positions shown in FIG. 1. In either horizontal position of the handle and spotlight 2, rotation of the grip 5 about its own axis rotates the spotlight 2 about a horizontal axis B in an up-down or “tilt” direction. Rotation of the grip 5 when the spotlight 2 and grip 5 are in a vertical orientation results in a left-right (pan) movement of the spotlight 2, while rotation of the grip 5 when the spotlight 2 and grip 5 are in a horizontal orientation results in an up-down “tilt” movement of the spotlight 2.
A combination of lateral and rotational forces applied to the grip 5 allows the user to direct the spotlight 2 in a broad range of directions relative to the vehicle. This control mechanism is a non-intuitive, but serviceable user interface in which the “pan” and “tilt” axes movement of the spotlight are interdependent. This results in a complex mathematical relationship between the direction of the spotlight and movements of the two shafts to produce an intended direction of the spotlight. Personnel operating the mechanical spotlights have learned how to apply rotational movements to the two rotational axes of the control mechanism to obtain the desired spotlight direction, but the movements are not at all intuitive.
The mathematical relationship between the direction of the spotlight and the position of the inner and outer shafts of the control mechanism can be described as follows:
                                          LAMP                                                              A                z                            =                              AZIMUTH                ⁢                                                                  ⁢                ANGLE                                                                                                                                                                  E                L                            =                              ELEVATION                ⁢                                                                  ⁢                ANGLE                                                                          HANDLE                                              INNER              =                              INNER                ⁢                                                                  ⁢                SHAFT                ⁢                                                                  ⁢                ANGLE                                                                                                                                                  OUTER              =                              OUTER                ⁢                                                                  ⁢                SHAFT                ⁢                                                                  ⁢                ANGLE                                                                                                                  A          Z                =                  INNER          ·                      COS            ⁡                          (              OUTER              )                                                  1                                    E          L                =                  INNER          ·                      SIN            ⁡                          (              OUTER              )                                                  2                          OUTER        =                              TAN                          -              1                                ⁡                      (                          EL              Az                        )                                      3                          INNER        =                                            EL                              COS                ⁡                                  (                  OUTER                  )                                                      ⁢                                                  ⁢            if            ⁢                                                  ⁢            outer                    ⁢                                          <                                          >                                          ⁢                      90            ,            270                                      4                  or                                                      INNER        =                                            Az                              SIN                ⁢                                                                  ⁢                                  (                  OUTER                  )                                                      ⁢                                                  ⁢            if            ⁢                                                  ⁢            outer                    ⁢                                          <                                          >                      0            ,            180                                      5      Equations 1 and 2 define the relationship between the handle and light when the light is driven by the handle from inside the vehicle (normal operation). Equations 3, 4 and 5 define the relationship between the handle and light when the handle is driven by the light (the light is grasped and moved directly from outside the vehicle).
In this control configuration, the up-down “tilt” movement of the light generated by rotation of the inner shaft is dependent upon the rotational position of the outer shaft, as shown in equations 4 and 5 above and FIG. 1. While this prior art control mechanism was effective for many years, changes in vehicle design and increased emphasis on vehicle safety are driving the need for new spotlight control devices and methods.
Vehicles are now being manufactured with structural members formed of tougher materials, such as alloy steels that make drilling a hole very difficult. Further, the A-pillar structural member has become smaller in cross section and manufacturers are wary of allowing third parties to make holes in functional parts of the vehicle safety cage.
There is a need for a spotlight control mechanism that does not require forming a hole in a vehicle structural member. There is also a need for a spotlight control mechanism that resembles the look and feel of the traditional mechanical control mechanism, so police and other first responders will intuitively know how to direct the spotlight. There is also a need for a spotlight control mechanism that improves over the traditional mechanical control mechanism.